std::is_placeholder
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| Definido no cabeçalho <functional>
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| template< class T > struct is_placeholder; |
(desde C++11) | |
Se
T é o tipo de um espaço reservado padrão (_1, _2, _3,...), então este modelo é derivado do std::integral_constant<int,1>, std::integral_constant<int,2>, std::integral_constant<int,3>, respectivamente. Se T não é um tipo de espaço reservado padrão, este modelo é derivado do std::integral_constant<int,0>.Original:
If
T is the type of a standard placeholder (_1, _2, _3, ...), then this template is derived from std::integral_constant<int,1>, std::integral_constant<int,2>, std::integral_constant<int,3>, respectively. If T is not a standard placeholder type, this template is derived from std::integral_constant<int,0>.The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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O modelo pode ser especializado para qualquer tipo definido pelo usuário, que deve ser tratada por std::bind como se fosse um espaço reservado para os argumentos não ligados.
Original:
The template may be specialized for any user-defined type which should be treated by std::bind as if it was a placeholder for unbound arguments.
The text has been machine-translated via Google Translate.
You can help to correct and verify the translation. Click here for instructions.
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Índice |
Herdado de std::integral_constant
Member constants
| value [estática] |
placeholder value or 0 for non-placeholder types (membro estático público constante) |
Member functions
| operator int |
converte o objeto em int, retorna value Original: converts the object to int, returns value The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (função pública membro) |
Member types
| Tipo
Original: Type The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. |
Definition |
value_type
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int
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type
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std::integral_constant<int, value> |
[editar] Exemplo
#include <iostream> #include <type_traits> #include <functional> struct My_2 { } my_2; namespace std { template<> struct is_placeholder<My_2> : public integral_constant<int, 2> {}; } int f(int n1, int n2) { return n1+n2; } int main() { std::cout << "Standard placeholder _5 is for the argument number " << std::is_placeholder<decltype(std::placeholders::_5)>::value << '\n'; auto b = std::bind(f, my_2, 2); std::cout << "Adding 2 to 11 selected with a custom placeholder gives " << b(10, 11) << '\n'; }
Saída:
Standard placeholder _5 is for the argument number 5 Adding 2 to 11 selected with a custom placeholder gives 13
[editar] Veja também
| (C++11) |
se liga um ou mais argumentos para um objeto de função Original: binds one or more arguments to a function object The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (modelo de função) |
| (C++11) |
espaços reservados para os argumentos não ligados em uma expressão de std::bind Original: placeholders for the unbound arguments in a std::bind expression The text has been machine-translated via Google Translate. You can help to correct and verify the translation. Click here for instructions. (constante) |
